The project includes studies on medical ecology, and the zoogeography, evolution and systematics of fleas, and is primarily based upon collections made during investigations on vectors and reservoirs of rickettsial and viral investigations undertaken in New Guinea, Ethiopia, Burma, Pakistan and other areas. Fleas and other ectoparasites are important in medicine not only as vectors of diseases, but because their study contributes to our understanding of the historical biogeography, distribution, and ecology of mammals and birds, and hence with the infections harbored or transmitted by such hosts. For example, it was because of the demonstrated affinities and zoogeography of fleas, chiggers and rodents that members of this Department sought, and found, scrub typhus and tick typhus in totally unexpected geographical regions and habitats in Pakistan. This "faunal approach" led to 1) predictions, since confirmed, of the occurrence of certain infections in parts of the USSR, Pakistan, India, China and Indo-China, and 2) to the hypothesis that the infections acquired by man from other animals are actually almost all transmitted from mammals that are higher in the evolutionary scale (e.g. ruminants, rodents), instead of from those lower down (e.g. bats, marsupials and insectivores). These concepts have led to some significant generalizations about the ecology of murine typhus and Korean hemorrhagic fever. During the next year, intensive study will be continued on the distribution, host relationships, phylogeny and systematics of fleas. Papers will be prepared primarily on the systematics of the Pygiopsyllidae, the major representative of the Order in the Australian Region, and on some Ethiopian fleas, as well as on Leptopsyllids.